An Experimental Study of the Effects of Rare Earths on Animal Lungs

Our plain-English summary of An Experimental Study of the Effects of Rare Earths on Animal Lungs, by G.W.H. Schepers, A. Delhant, A.J. Redlin (1955).

The study

• Authors: G.W.H. Schepers, A. Delhant, A.J. Redlin
• Published: P.292-295 (1955)
• Type of article: Journal article
• Our copy: from Johns-Manville's own medical library. The article is still under copyright, so we describe it here rather than post it.

In plain English

This article is not about asbestos. It reported an animal experiment at the Saranac Laboratory on rare earth dusts. The work was begun by Dr. Gardner after X-ray changes were found in Fostoria, Ohio, workmen exposed to rare earth oxide and fluoride dusts. Two assistants completed it after Gardner died. In all, 93 guinea pigs received one of two rare earth blends mixed with carbon and potassium sulfate. One blend was high in rare earth oxides, the other in rare earth fluorides. Both were injected into the windpipe; the fluoride-rich blend was also inhaled. Some animals died of pneumonia soon after injection, possibly partly due to the chemicals, the authors thought. Injected lungs showed large, black, soft to slightly firm masses; no metastatic foci of reaction appeared in other organs. In the inhalation study, lung-lining pigmentation increased over time, and chemical analysis showed rare earths steadily accumulating in the lungs. Based on this naked-eye examination, the authors concluded that the blends acted as relatively inert substances; they said the precise tissue response required microscopic analysis, reported elsewhere.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Animal experiment: intratracheal injection studies with two rare earth blends, plus a long-term inhalation study with one blend. Only the gross (visible to the eye) findings are reported here.
• Who was studied: 93 guinea pigs at the Saranac Laboratory. The study was prompted by radiological changes in workmen from Fostoria, Ohio, exposed to rare earth dusts.
• Exposure: Two blends of rare earths with carbon and potassium sulfate. One had a relatively high proportion of rare earth oxides and the other a high rare earth fluoride content. Both were given by intratracheal injection, and the fluoride-rich blend was also given by inhalation. No asbestos was studied.
• Main results:
  • Intratracheal groups: three guinea pigs given the oxide-rich mixture, and four given the fluoride-rich mixture, died of pneumonia shortly after injection. The authors thought these deaths may have been at least partly due to the chemicals introduced.
  • Intratracheal groups: two animals from the first group and one from the second later died of rodent typhoid, which affected the whole laboratory animal population.
  • Intratracheal groups: lungs showed large, black, soft to slightly firm conglomerate lesions, commonest in the caudal lobe. Few differences were seen over the 540-day period, and there were no metastatic foci of reaction in any other organ.
  • Inhalation study: the casualty rate was comparatively high, with 25 guinea pigs dying of intercurrent causes, mostly apparently pneumonia. The remaining animals were killed in groups of three at intervals.
  • Inhalation study: gross examination showed ever-increasing pleural pigmentation, going from pale gray to black. No comparable lesions occurred in any other organ.
  • Inhalation study: chemical analysis of the lungs showed a progressive accumulation of rare earth compounds in lung tissue, matching the increasing pigmentation.
• The authors' conclusion: The authors concluded that, on gross observation, the two rare earth blends acted as relatively inert substances. They noted that the precise tissue response becomes apparent only when the microscopic features are analyzed, and these are reported elsewhere.
• Limitations the authors state:
  • The authors note that the precise nature of the lung tissue response becomes apparent only from microscopic (histological) analysis, which this paper does not present.
  • The authors note that after three years in a dust chamber, normal aging would begin to influence the death rate.

Topics

Medical terms in this study, explained in our Lexicon: Saranac Laboratory.

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